The formation and processing of large program guides conveying information concerning potentially thousands of broadcast program channels covering a wide geographic area poses a number of problems. The geographic area covered may encompass the whole of the USA or whole continents, for example, and large quantities of information may have to be acquired, collated, encoded and broadcast in a format that facilitates subsequent decoding of the broadcast material. The bandwidth required to process such large quantities of information expands in proportion to the quantity of information being processed. Therefore, there is a need to structure program guide data in order to optimize the use of the available bandwidth.
The degree to which the program guide data structure may be optimized is constrained by the cost of a decoder unit for receiving the structured data. In fact there is a compromise to be made between transmission bandwidth and decoder complexity. At one extreme of the compromise, all duplicative and redundant data elements in the program guide information are eliminated in order to minimize the required transmission and processing bandwidth. As a result, each decoder needs to receive, buffer, parse and collate information from an entire program guide datastream, thereby necessitating a complex and costly decoder.
At the other extreme of the compromise, the program guide information is partitioned into individual sub-sets tailored to the requirements of a particular User or group of Users. This means that each decoder needs to receive, buffer, parse and collate targeted information containing minimal redundancy which facilitates employing a simpler, more economical decoder requiring less processing power. However, such partitioning requires a larger transmission bandwidth to accommodate the increased information redundancy resulting from the need to incorporate duplicate program guide information items in multiple different program guide sub-sets corresponding to different partitions. The problems involved in processing large quantities of program guide information and in achieving a desirable compromise between transmission bandwidth and decoder complexity are addressed by a system according to the present invention. Derivative problems involved in structuring and partitioning program guide data to facilitate both decoding and selectable program guide generation by a decoder are also addressed by a system according to the invention.